Direct conversion receivers (DCR) are employed for processing incoming signals, such as, RF signals. In typical operation, an RF signal is received by a pre-selector filter which may be a bandpass filter to reject spurious out-of-band signals. A filtered RF signal is passed into a low-noise amplifier (LNA) which amplifies the filtered RF signal. The amplified RF signal is then passed through an in-phase path and a quadrature-phase path for further processing.
Typically, the in-phase path includes a mixer and a filter. Similarly, the quadrature-phase path also includes a mixer and a filter. The mixers and the filters in the in-phase path and the quadrature-phase path down convert the RF signal to baseband. The mixers in typical DCRs may encounter low frequency noise and direct current (DC) offset error at baseband, due to non-ideal behavior of the mixers.
Chopping based DCRs are used to invert phases of mixer input and output signals in the in-phase path and quadrature-phase path, thereby mitigating the low frequency noise and the DC offset error at baseband. Chopping is controlled by a chopping signal generator. The controlling of the periodicity of the chopping signal may be used to shift non-idealities associated with the mixers away from a signal of interest at baseband. However, the inversion of the phase of the LO signal using a chopping signal may lead to the generation of LO signals bearing undesired short duration pulses and high frequency components. The undesired short duration pulses may lead to additional switching resulting in increased power dissipation.
Accordingly, there is a need for precluding undesired short duration pulses and high frequency components in LO signals.